dcb-rewr(8) — Linux manual page


DCB-REWR(8)                       Linux                      DCB-REWR(8)

NAME         top

       dcb-rewr - show / manipulate the rewrite table of the DCB (Data
       Center Bridging) subsystem

SYNOPSIS         top

       dcb [ OPTIONS ] rewr { COMMAND | help }

       dcb rewr  {  show  |  flush  }  dev DEV [ prio-dscp ] [ prio-pcp

       dcb rewr  {  add  |  del  |  replace  }  dev DEV [ prio-dscp
               DSCP-MAP ] [ prio-pcp PCP-MAP ]


       DSCP-MAPPING := PRIO:{ DSCP | all }



       DSCP := { 0 .. 63 }

       PCP := { 0(nd/de) .. 7(nd/de) }

       PRIO := { 0 .. 7 }

DESCRIPTION         top

       dcb rewr is used to configure the rewrite table, in the DCB (Data
       Center Bridging) subsystem.  The rewrite table is used to rewrite
       certain values in the packet headers, based on packet priority.

       DCB rewrite entries are, like DCB APP entries, 3-tuples of
       selector, protocol ID, and priority. Selector is an enumeration
       that picks one of the prioritization namespaces. Currently, only
       the DSCP and PCP selector namespaces are supported by dcb rewr.

       The rewrite table is a list of DCB rewrite rules, that applies to
       packets with matching priority.  Notably, it is valid to have
       conflicting rewrite assignment for the same selector and
       priority. For example, the set of two rewrite entries (DSCP, 10,
       1) and (DSCP, 11, 1), where packets with priority 1 should have
       its DSCP value rewritten to both 10 and 11, form a well-defined
       rewrite table.  dcb rewr tool allows low-level management of the
       rewrite table by adding and deleting individual rewrite 3-tuples
       through add and del commands. On the other hand, the command
       replace does what one would typically want in this
       situation--first adds the new configuration, and then removes the
       obsolete one, so that only one rewrite rule is in effect for a
       given selector and priority.

COMMANDS         top

       show   Display all entries with a given selector. When no
              selector is given, shows all rewrite table entries
              categorized per selector.

       flush  Remove all entries with a given selector. When no selector
              is given, removes all rewrite table entries.

       del    Add and, respectively, remove individual rewrite 3-tuples
              to and from the DCB rewrite table.

              Take the list of entries mentioned as parameter, and add
              those that are not present in the rewrite table yet. Then
              remove those entries, whose selector and priority have
              been mentioned as parameter, but not with the exact same
              protocol ID. This has the effect of, for the given
              selector and priority, causing that the table only
              contains the protocol ID (or ID's) given as parameter.

PARAMETERS         top

       The following table shows parameters in a way that they would be
       used with add, del and replace commands. For show and flush, the
       parameter name is to be used as a simple keyword without further

       prio-dscp DSCP-MAP
              DSCP-MAP uses the array parameter syntax, see dcb(8) for
              details. Keys are priorities, values are DSCP points for
              traffic with matching priority. DSCP points can be written
              either directly as numeric values, or using symbolic names
              specified in /etc/iproute2/rt_dsfield (however note that
              the file specifies full 8-bit dsfield values, whereas dcb
              rewr will only use the higher six bits).  dcb rewr show
              will similarly format DSCP values as symbolic names if
              possible. The command line option -N turns the show
              translation off.

       prio-pcp PCP-MAP
              PCP-MAP uses the array parameter syntax, see dcb(8) for
              details. Keys are priorities. Values are PCP/DEI for
              traffic with matching priority. PCP/DEI values are written
              as a combination of numeric- and symbolic values, to
              accommodate for both. PCP always in numeric form e.g 0 ..
              7 and DEI in symbolic form e.g 'de' (drop-eligible),
              indicating that the DEI bit is 1 or 'nd' (not-drop-
              eligible), indicating that the DEI bit is 0.  In
              combination 1:2de translates to a mapping of priority 1 to
              PCP=2 and DEI=1.

EXAMPLE & USAGE         top

       Add a rule to rewrite DSCP to 0, 24 and 48 for traffic with
       priority 0, 3 and 6, respectively:

       # dcb rewr add dev eth0 prio-dscp 0:0 3:24 6:48

       Add a rule to rewrite DSCP to 25 for traffic with priority 3:

       # dcb rewr add dev eth0 prio-dscp 3:25
       # dcb rewr show dev eth0 prio-dscp
       prio-dscp 0:0 3:CS3 3:25 6:CS6
       # dcb -N rewr show dev eth0 prio-dscp
       prio-dscp 0:0 3:24 3:25 6:48

       Reconfigure the table so that only one rule exists for rewriting
       traffic with priority 3.

       # dcb rewr replace dev eth0 prio-dscp 3:26
       # dcb rewr -N show dev eth0 prio-dscp
       prio-dscp 0:0 3:26 6:48

       Flush all DSCP rules:

       # dcb rewr flush dev eth0 prio-dscp
       # dcb rewr show dev eth0 prio-dscp

       Add a rule to rewrite PCP to 1 and DEI to 0 for traffic with
       priority 1 and a rule to rewrite PCP to 2 and DEI to 1 for
       traffic with priority 2:

       # dcb rewr add dev eth0 prio-pcp 1:1nd 2:2de
       # dcb rewr show dev eth0 prio-pcp
       prio-pcp 1:1nd 2:2de

EXIT STATUS         top

       Exit status is 0 if command was successful or a positive integer
       upon failure.

SEE ALSO         top

       dcb(8) dcb-app(8) dcb-apptrust(8)

REPORTING BUGS         top

       Report any bugs to the Network Developers mailing list
       <netdev@vger.kernel.org> where the development and maintenance is
       primarily done.  You do not have to be subscribed to the list to
       send a message there.

AUTHOR         top

       Daniel Machon <daniel.machon@microchip.com>

COLOPHON         top

       This page is part of the iproute2 (utilities for controlling
       TCP/IP networking and traffic) project.  Information about the
       project can be found at 
       If you have a bug report for this manual page, send it to
       netdev@vger.kernel.org, shemminger@osdl.org.  This page was
       obtained from the project's upstream Git repository
       ⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
       2024-06-14.  (At that time, the date of the most recent commit
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iproute2                       15 may 2023                   DCB-REWR(8)

Pages that refer to this page: dcb(8)